Physical properties of materials are dictated by the hierarchical arrangements of atoms, molecules, and supramolecular assemblies across different length scales. The construction and engineering of structures at each length scale, especially at the 2- to 100-nm scale, are critically important in achieving desired macroscopic properties. As the traditional top-down lithography techniques face serious challenges in fabricating 2D and 3D nanostructured materials with sub-20-nm feature sizes, the bottom-up approach based on self-organization or directed assembly of functional molecules provides a promising alternative. The past decades have witnessed the development of diverse self-assembly building blocks ranging from small-molecule surfactants, block copolymers, and dendrimers to DNAs, peptides, and proteins. Notably, these motifs have enabled the programmed self-assembly of nanomaterials as demonstrated in DNA-coated nanoparticles. These studies have greatly improved the understanding of thermodynamics and kinetics of self-assembly processes and have opened enormous possibilities in modern nanotechnology.
Noncovalent interactions, such as hydrogen bonding, amphiphilic effect, π-π interaction, metal coordination bonding, and electrostatic forces are known to be the fundamentals to precise self-assembly. Specific recognition and binding events, such as DNA hybridization and protein folding, are based on collective and cooperative multiple secondary interactions. More recently, anisotropy in shape has also been recognized as a critical factor in the self-assembly process due to packing constraints, as indicated by the emerging concept of “shape amphiphiles”. However, it remains challenging to design nanomaterials “from scratch” that can generate diverse structures at a specific length scale, e.g., the nanostructures with feature sizes around 100 nm or smaller and even heretofore never produced sizes of 10 nm or smaller, as in the case of some embodiment of the invention herein.
Small-molecule surfactants have been a classic type of self-assembling materials and are typically composed of polar ionic heads and flexible hydrophobic tails. Although a variety of nanostructured assemblies can be created, they usually lack the required etching contrast between the hydrophobic and hydrophilic domains. The well-established microphase separation of block copolymers has, on the other hand, led to the development of the block copolymer lithography, affording access to nanopatterning with high patterning density at low processing costs. Substantial progress has been demonstrated to guide the nanostructure formation in the block copolymer thin films at a 20- to 100-nm feature size scale. Pushing the feature sizes to an even smaller scale has had limited success. It is difficult to achieve a strong segregation with a sharp interface at sub-20-nm length scale, because the chemical incompatibility in typical block copolymers is reflected by the product of the interaction parameters and the degree of polymerization. It is even more challenging to generate unconventional patterns, such as rectangular lattices, due to their thermodynamic metastability. Micro-phase separation of block copolymer materials has been well documented. The ability of bock copolymers to generate various ordered patterns in the bulk and thin film states serves as the basis for the development of alternative nanopatterning technologies to complement the traditional “top-down” photolithographic processes, especially in creating small feature sizes (below 100 nm) at large area.
In the present invention size amplification and structural diversification of self-assembling small-molecule surfactants, is seen as an effective strategy for the molecular design of a unique class of self-assembling “giant surfactants”. This class of giant surfactants bridges the gap between small molecule amphiphiles and amphiphilic block copolymers and possesses advantages of both materials, thus providing a unique platform for engineering versatile nanostructures that, in some embodiments, can achieve sub-10-nm feature sizes, though the present invention is not limited thereto.